BEIJING (Reuters) - Beijing’s mayor Cai Qi has been appointed party chief of the capital city, the official Xinhua news agency reported on Saturday.

Cai is close to Chinese President Xi Jinping, sources with ties to the leadership have told Reuters, and is virtually assured a seat in the decision-making politburo during the 19th party congress in the autumn.

The politburo currently has 25 members.

Cai and Xi overlapped during their time in various government positions both in the eastern province of Zhejiang and in the southeastern province of Fujian.

This is the latest move by Xi to put his allies in key positions ahead of the party congress.

In the past, politicians served as provincial governors or city mayors for five years before being promoted to party secretary of the province or city. The party secretary outranks the governor or mayor.

Cai has been promoted quickly, as he only became the acting mayor of Beijing in October last year and the mayor in January this year.

Prior to becoming the acting Beijing mayor, Cai was a senior official at China’s National Security Commission.

China’s environment minister Chen Jining will replace Cai as acting Beijing mayor, Xinhua reported in a separate story on Saturday.